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Uranus


Uranus is a frigid world tipped on its side; most other large planets spin more or less in the same direction that the Sun does, but some event early in Uranus' history tipped its spin axis all the way over, past the horizontal. It has long been thought that the tilt resulted from a giant collision, but recently it has been suggested that the tilt was caused by complex gravitational interactions between the giant planets as they formed and migrated to their current positions.

Its crazy tilt notwithstanding, Uranus has had the unfortunate reputation of being the most boring planet in the solar system; its serene blue methane haze displayed few details to Voyager 2's cameras. But with northern hemisphere spring now arriving at Uranus, new cloud patterns have blossomed across the planet, punching through the haze.

Uranus is surrounded by 11 very faint rings. It has five large icy satellites: Miranda, Ariel, Umbriel, Titania, and Oberon. A clutter of small moons orbits Uranus within the orbit of Miranda, and a swarm of (probably) captured bodies flies around the planet outside Oberon's position.

May 2, 2007 through February 20, 2008 heralded an exciting time for Uranus scientists. Uranus experienced its equinox on December 7, 2007, with the Sun coming to its north pole for the first time in 42 years. And on May 2, August 16, and February 20, Earth crossed Uranus' ring plane.

Uranus has only been visited by one spacecraft, Voyager 2. More recently, it has been observed by the Hubble Space Telescope and the Adaptive Optics-equipped Keck II telescope. No future missions are currently planned to visit Uranus.

Uranus Numbers
Size: 3rd largest planet - 51,118 kilometers -- 4.007 Earths
Calendar: 1 Uranus year = 83.749 Earth years; 1 Uranus day = 0.72 Earth days
Orbit: 2,872,460,000 km - 19.201 Earth orbits
Axial tilt: 97.77 degrees (retrograde, and tilted almost horizontal)